1. Field of the Invention
A technique disclosed herein relates to a control apparatus for a turbocharged (turbo-supercharged) diesel engine, particularly, a control at start of an automatically-stopped diesel engine.
2. Description of the Background Art
A control apparatus for a turbocharged diesel engine is described, for example, in JP 2003-120353A. In order to solve a problem that, in the event of a demand for vehicle acceleration, an increase in air intake amount fails to follow an increase in fuel injection amount due to delay in speed rise of a turbocharger to cause deterioration in exhaust emission values, the control apparatus is configured, in response to the demand for vehicle acceleration, to perform a post injection following a main injection, to increase exhaust gas energy so as to promote a speed rise of the turbocharger.
Meanwhile, as measures for improvement in fuel economy, reduction in CO2 emissions, etc., there has been a so-called idle stop system designed, for example, to automatically stop an engine when a given engine stop condition is satisfied during a temporary stop of a vehicle, and then restart the engine when a given engine restart condition is satisfied. Therefore, it is contemplated to employ such an idle stop system in the above turbocharged engine.
In the idle stop system, the engine restart condition is roughly classified into a first engine restart condition associated with a demand for vehicle start, to be satisfied, for example, when a driver depresses an accelerator pedal, and a second engine restart condition nonassociated with the demand for vehicle start, to be satisfied when a vehicle system's demand nonassociated with the demand for vehicle start occurs, for example, when an SOC (State-of-Charge) of a battery becomes lower than a predetermined value, or when an activation of a compressor for an air-conditioning system becomes necessary.
In the above two cases, when the engine restart condition nonassociated with the demand for vehicle start is satisfied, it is desirable to complete an engine start-up within a short period of time, and, after completion of the engine start-up, stand by for issue of the demand for vehicle start, according to depression of an accelerator pedal by a driver, etc. On the other hand, when the engine restart condition associated with the demand for vehicle start is satisfied, it is necessary not only to complete an engine start-up within a short period of time but also to allow a vehicle to be started and accelerated just after completion of the engine start-up. During this control, in view of achieving enhanced vehicle start/acceleration performance, it is desirable that turbocharging is promptly initiated. As above, a need during engine start in response to satisfaction of an engine restart condition varies depending on the presence or absence of the demand for vehicle start.